This invention relates to Fe-base sintered alloys for valve seats for use in internal combustion engines in which light oil, LPG, or the like is used as a fuel, and a method of manufacturing same, and more particularly to Fe-base sintered alloys of this kind which possess high strength and high hardness and hence exhibit excellent abrasion resistance as well as excellent lubricity, and a method of manufacturing same.
Conventionally, various kinds of Fe-base sintered alloys have widely been used for the production of valve seats for use in internal combustion engines. However, these conventional Fe-base sintered alloys have too low density and are hence too porous to provide a valve seat formed thereof with satisfactory strength. To provide sufficient strength for valve seats formed of the conventional Fe-base sintered alloys, usually Cu, Pb, or the like are infiltrated into the surfaces of the valve seats so as to seal the pores with the Cu, Pb or the like. However, even if such sealing is applied to the valve seats, the conventional sintered alloys themselves have hardness insufficient for use as the valve seats and are liable to get abraded particularly when a fuel with low lubricity is used in the engines.
The tendency of abrasion of the alloys has become more conspicuous as internal combustion engines with higher performance have been developed and operated under more severe operating conditions.